I can definitely do this. Just completed Episode 2 of Spartan Ops, finished Solo Legendary yesterday, and I'm still reading through The Thursday War (though I've read ALL books prior to that). I can do this. Only thing is, would you like to include Kelly, Fred, Linda? I've always wanted to see Chief reunited with them, and I can play any - I have a feeling they'll be included in Halo 5 and 6, anyways.
EDIT: And while I'm always up for OCs, are canons allowed? Not going to lie, I think I can play a mean Sarah Palmer. She's a great character, and I am a fan of including multiple characters from the stories - both original and existing.